Cardiomyocytes derived from human induced pluripotent stem cell (hiPSC-CMs) can serve as an abundant and ethical source of cardiomyocytes (CM) for developmental and pharmacological studies, and can also be used for patient-specific therapeutics. Unfortunately, newly differentiated hiPSC-CMs differ from adult CMs on both a structural and functional level. In order to achieve the full potential of hiPSC-CMs, these cells need to be matured into a phenotypic state that more closely resembles the adult one. Long-term culture of hiPSC-CMs has been shown to significantly increase their structural and functional traits, but we need to fin alternative methods that accelerate their maturation rates. Previous studies on neonatal rat ventricular CMs and embryonic stem cell derived CMs have shown that mechanical cues, such as substrate stiffness and stretch, hasten CM maturation. Physiologically, substrate stiffness can be related to the synthesis of extracellular matrix proteins in the myocardium that stiffen the tissue. Likewise, substrate stretch can be related to the creep strain that individual CMs experience during hypertrophic growth and from the cyclic strain they experience during the cardiac cycle. The observed maturation of CMs to substrate stiffness and stretch implies the importance of mechanotransduction, i.e. the process of a cell sensing and responding to mechanical stimuli. Integrins act as an initial sensing structure in this mechanotransductory pathway. Integrins are transmembrane proteins that attach selectively to the extracellular matrix (ECM), based on a specific combination of ? and ? subunits. It is widely regarded that integrins are responsible for translating external mechanical stimuli across the cell membrane, after which downstream intracellular signaling, leading to CM maturation, can ensue. It has been observed, for example, that the ?1 subunit plays a key role in heart development; however such studies have not been performed on the cellular level for hiPSC-CMs. In this fellowship, I will study the mechanisms that lead to the maturation of hiPSC-CMs by mechanical stimuli. The overall hypothesis is that mechanotransduction pathways initiated at integrins lead to the maturation of hiPSC-CMs. Specifically, I will focus on the role of several key integrins - the ?1 subunit, ?1?1, ?6?1, ?5?1, ?v?3, and ?v?5 - in this mechanotransductory response. The lon-term impact of this effort will be to understand and therefore control the maturation of hiPSC-CMs for cardiology studies and therapeutics.